In Drupal I have two image fields, one to act as a thumbnail and the other the image that will open when the thumbnail is clicked. The only way I could find to link the two was to use the option for "Output this field as a link" and link to the image field.

This works, so when I click the thumbnail it opens the larger image however I would like to use lightbox2 for this task but in the "Output this field as a link" options there is no way to set the "rel" attribute.

Is there a way to either set the rel attribute or invoke the lightbox by setting a class?